TODAY’S STUDY: WHAT BURNING WOODY BIOMASS CAN (AND CAN’T) DO IN NEW ENGLAND

Between the people in the energy community who will burn any cheap thing to generate power, no matter how dirty, and those who will burn “not nothing, not no-how,” there are those who see in sustainable forestry an opportunity that spreads across a spectrum of benefits.

Using forest waste wisely as biomass to generate electricity – if that is not an oxymoron – would provide a local source of supply to the grid, grow a domestic energy sector and establish a potentially “carbon-neutral” power stream.

On the other hand, some studies have questioned whether the burning of biomass can be carbon neutral and there are doubts about the wisdom of building an infrastructure based on a questionable resource of limited capacity. The study highlighted below found that in New England the forest biomass resource is even more limited than had previously been thought.

An energy community debating such questions is a good thing. A free and informed dialogue, though often heated, holds the best hope of arriving at the right way forward. This study adds substantial fuel to the debate’s fire.

Forest Biomass and Bioenergy: Opportunities and Constraints in the Northeastern United States
Thomas Buchholz, Charles D. Canham and Steven P. Hamburg, February 17, 2011 (Cary Institute of Ecosystem Studies)

Executive Summary

There has been enormous interest in the use of forest biomass for energy in the Northeastern US. Both the federal government and most states in the region are actively engaged in assessments of the potential role of forest biomass in renewable energy standards and portfolios. This study addressed two critical components of those assessments:

• the amount of biomass that can be sustainably harvested from Northeastern forests for energy purposes, and

• which conversion technologies and end‐use applications should be pursued to most effectively reduce greenhouse gas emissions, reduce dependence on foreign oil, and promote the rural economy of the region.

Our analyses relied on data on forest biomass supply from the U.S.D.A. Forest Service Forest Inventory Analysis (FIA) program and the Timber Products Output (TPO) database, and on data from the Energy Information Administration (EIA) for the energy analysis.

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Our analyses yield significantly lower estimates of the sustainable supply of biomass feedstocks from Northeastern forests than the estimates from a number of previous studies. The primary reasons for the differences are due to differences in:

• Estimates of forest productivity: many previous studies use values for forest biomass productivity from a limited number of research sites, and those estimates are typically higher than estimates derived from a fuller analysis of the network of FIA plots across each state. The most likely reason for the difference is that the more localized studies sample forests on sites that are more productive, on average, than the forestland base as a whole.

• Estimates of the available forestland base: recent studies have made a wide range of assumptions about how biological, physical, legal, social, and economic factors limit the amount of the region’s forestland that is available for harvest. There is still a great deal of uncertainty about a number of these factors. We present a range of scenarios of sustainable biomass supply given explicit assumptions about the magnitudes of different constraints on the available forestland base.

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Estimating forest biomass availability for energy production in the Northeast

• Forestland makes up slightly over 67% of the total land area of the northeastern states. While the area of forestland has increased significantly over the past century, recent studies suggest that the current forestland base represents a high‐water mark, and is unlikely to increase.

• Despite assumptions that northeastern forests are even‐aged, maturing, and declining in growth rates, the data show a very different picture, with (a) forests managed primarily by partial harvesting (rather than clearcutting), (b) stands with a wide range of tree biomass, and (c) a landscape that is very close to optimal in terms of net forest growth and accumulation of carbon in aboveground tree biomass.

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• Timber harvests during recent years (2004‐2008) have been below net growth calculated over the entire forestland base (63% of net growth over the entire region, but with significant variation from state to state). Both the sustainability of the current harvest rates, and the degree to which harvest rates could be sustainably increased for biomass energy production, however, depend critically on the fraction of the total forestland base that is available for harvests.

• Less than 6% of the region’s forestlands are legally reserved from harvests, but a wide variety of biophysical, economic and social constraints place additional limits on the forestland base that is available for harvest. Two of the potentially most significant of these are (a) parcelization – the subdivision of forestland into small land holdings that are too small for efficient harvest operations, and (b) landowner unwillingness to harvest because of higher priority interests. Unfortunately, there is a great deal of uncertainty about the impact of both of these factors on the available forestland base.

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The magnitude of this uncertainty can be underlined by the fact that 10% of all unreserved forest land is located in private parcels of under 8 ha (20 acres).

• We considered two sets of assumptions about the magnitudes of the biophysical, economic and social constraints on the available forestland. Under our conservative (“Low”) scenario, only 63% of the total northeastern forestland is available for harvests (with substantial variation from state to state), and recent harvest rates have consumed effectively all of the sustainable yield. However the recent harvests recover only a small fraction of logging residue, and some additional fraction of this material could be harvested sustainably for biomass energy. Under a much less restrictive set of assumptions (our “High” scenario) – in which 78% of the forestland base is available for harvest, recent harvests represent only 82% of total net growth on available forestland, and there is a more significant potential for additional harvests for biomass energy, though the most advantageous strategy is to produce additional wood products where possible and use the remainder for bioenergy.

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• We used these different sets of assumptions about the area of available forestland, and whether biomass currently used by the pulp and paper industry would be diverted to energy production, to calculate a set of 5 different scenarios for the sustainable quantity of biomass that could be harvested and devoted to energy production in the region (in metric tons of dry biomass, per year) (Table 4). Three of the scenarios assume that all of the current pulp wood harvests would be dedicated to biomass energy supply, which would cause additional carbon emissions (leakage) in regions outside the Northeast to make up for the lower local supply of biomass for pulp and paper products.

• If (a) all current pulp harvests are diverted to biomass energy use, and (b) recent harvest rates are increased to the point where they meet recent forest net growth (a limited but intuitive estimate of sustainability), under our two different sets of assumptions about forestland availability, we estimate that biomass production for energy use would range from 13.7 – 15.8 million metric tons per year over the 8‐state region (Pennsylvania – Maine, excluding New Jersey) (Table 4).

• If biomass currently used in the pulp and paper industry is not diverted to energy production, we estimate that the region can only sustainably produce 4.2 – 6.3 million metric tons/yr of biomass. This better reflects the potential for net reductions in greenhouse gas emissions (Table 4).

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Substituting Fossil Fuels with Biomass in the Northeast

• Assuming that all of the estimated sustainable forest biomass supply ‐ ranging from 4.2 – 15.1 million metric tons/yr under the different scenarios ‐ was used in the most efficient current technology (combined heat and power plants), forest biomass energy would constitute 1.4 – 5.5% of the entire region’s current energy consumption.

• The proportion of the energy portfolio contributed by forest biomass, however, would vary significantly among states, with a higher percentage in states with large forestland bases and low energy consumption.

• Biomass can be used in many different energy sectors and with different efficiencies.

Using the conservative estimate of 4.2 million metric tons of forest biomass supply for energy, the Northeast could either:

o Replace 6% of its coal consumption (used for electricity); or

o Provide 4 to 6% of its total electricity mix from biomass1, with an additional 14% replacement potential of the liquid fossil fuels used in the commercial and industrial heating sector if Combined Heat and Power (CHP) technology is used; or

o Replace 28% of the liquid fossil fuels used in the commercial and industrial heating sector; or

o Replace 16% of the liquid fossil fuels used in the residential heating sector; or

o Replace 5 or 2% of its current highway diesel or gasoline consumption, if future liquid transport biofuels become commercially available.

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• Replacing one metric ton of coal with biomass (e.g. by cofiring) is over three times more efficient in terms of endpipe CO2 emission reductions than substituting gasoline with cellulosic ethanol. Combined heat and power plants reduce close to five times more endpipe CO2 emissions when replacing coal (for electricity) and liquid fossil fuels (for heat) than substituting gasoline with cellulosic ethanol.

• Despite having limited if any potential for sustainable increases in timber harvests (over levels recorded from 2004‐2008), Maine shows the most promising fossil fuel substitution potential from increased recovery of logging residue. We estimate that Maine could replace up to 42% or 49% of its current use of liquid fossil fuels in the commercial/industrial or residential heating sector, respectively, through this source of biomass energy. New Hampshire also shows favorable substitution potentials across all scenarios. For instance, it could replace 84% of its current use of liquid fossil fuels in the industrial and commercial heating sector with local forest biomass if all biomass would be directed into that sector only. In comparison, our analyses suggest that neither Connecticut nor Rhode Island will be able to able to substitute >10% of any of their fossil fuel sectors (transport fuels, heating applications, electricity production) with forest‐based biomass energy.

• Understanding the net greenhouse gas implications of additional forest biomass harvests and its impacts on terrestrial carbon stocks in the region will require further analyses especially those related to the CO2 emissions of land use change associated with expanded harvesting activities (harvesting lands not currently being managed).

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• Results suggest that displacing oil with biomass in commercial and industrial boilers represents the most viable short‐term scenario for reducing dependence on foreign oil and net greenhouse gas emissions. Co‐firing biomass with coal in existing coal electrical generating plants may also be an efficient way to replace current fossil fuel use and curb CO2 emissions if residues are used – but it does nothing to reduce energy imports and risks a geographic mismatch of demand and availability. While cellulosic ethanol would require additional research and commercialization efforts, producing process heat in biomass boilers or co‐firing biomass with coal faces much lower technology hurdles. It could therefore be implemented within a much shorter timeline, requires less investment into new infrastructure, and has immediately favorable CO2 substitution efficiency if waste wood and logging residues are used.

• Forest‐based bioenergy can play an important role in a future diversified energy mix in the Northeast even under conservative assumptions about the magnitude of the biomass resource. However, for forest‐biomass derived bioenergy to matter significantly across all potential substitution scenarios, total energy demand has to be reduced dramatically by reducing overall energy consumption and increasing the efficiency of energy use, especially in the transport sector.

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All of the biomass energy technologies ‐ regardless of efficiencies, energy carrier substituted, conversion technology applied, or temporal scale of implementation ‐ rely on a cost‐efficient and pervasive biomass supply chain. The declining forest industry in the Northeast poses a major threat to the maintenance of both the physical infrastructure for forestry, and of the human resources for sound forest management (see e.g. Sherman 2007 for Vermont, Germain 2010 for New York). To spur innovation and investments in biomass supply infrastructure, there is a need for a reliable biomass market in the shortterm.

Supporting short‐term bioenergy applications now (such as use in commercial boilers) might therefore also contribute to the development of more long‐term technologies (such as wood‐fired distributed combined heat and power systems) that can be more attractive from an energy efficiency or CO2‐offset capacity point of view. This is a strategy that Austria has applied successfully since the 1980s by first supporting biomass heating applications and then expanding biomass use for electricity production (OEMAG 2010). As a result, Austria now provides 11% of its electricity from biomass.

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Conclusions

Forest biomass energy can play an important role in a diversified renewable energy portfolio for the Northeastern U.S., and can be an important source of jobs and economic growth in the region. Our analyses, however, show that the magnitude of the sustainable forest biomass supply is far smaller than most previous studies have suggested.

Policies to promote forest biomass energy need to recognize the wide range of biological, physical, social, and economic constraints on the sustainable supply of forest biomass for energy, in order to avoid perverse incentives that lead to unsustainably high rates of harvest. Overharvesting would lead to degradation of northeastern forests a resource of critical economic and ecological importance – and actually release more carbon to the atmosphere than would comparable energy production from fossil fuels.

The magnitude of a forest-based biomass energy industry in the Northeast will ultimately reflect the balance of the often competing demands that public and private landowners place on forests for economic, environmental, and aesthetic benefits.